Changes of arterial and venous blood flow velocities at retinal vessel bifurcations

Abstract

Purpose: To evaluate the changes of arterial and venous flow velocities at retinal vessel bifurcations

Methods: In 50 eyes of normal healthy subjects, retinal flow volume (RFV) and vessel diameters (d) at arterial and venous bifurcation were measured by laser speckle flowgraphy (LSFG). Blood flow velocity (BFv) index were calculated as RFV/d², and cross sectional area (S) index of each vessel was defined as d². The change of BFv index was defined as the ratio of BFv index in the daughter vessel (d-BFv) over that index in the trunk vessel (t-BFv), and the change of S index was also defined as S index in the daughter vessels over the trunk vessel (d-S/t-S).

Results: The ratio of RFV in the trunk vessel over the sum of the two daughter vessels was 1.06±0.09 in the artery and 1.02±0.1 in the vein. t-BFv index was 1.76±0.63 in the artery and 1.57±0.49 in the vein. t-S index was 12.1±2.06 in the artery, and 16.3±2.82 in the vein. In the daughter vessels, d-BFv was 76.9±12.7% of t-BFv in the artery, and 80.2±16.0% in the vein. d-S index was 70.3±19.7% of t-S in the artery, and 76.0±12.6% in the vein. d-BFv/t-BFv in the artery was correlated with d-S/t-S (r=0.464), while that in the vein was not correlated with d-S/t-S (r=0.067)

Conclusions: RFV by LSFG was found to be an appropriate index for retinal flow volume at retinal vessel bifurcation. Both blood flow velocities in the artery and vein were decreased after the vessel bifurcation, but the change of BFv was dependent upon the change of S in the artery but independent in the vein. Dynamic change of retinal flow at bifurcation was different in the artery and vein.

Keywords: 688 retina • 436 blood supply • 468 clinical research methodology